Each year approximately 300,000 coronary bypass procedures are performed in the United States. The typical treatment for small diameter artery replacement has been for surgeons to use the patient's own vessels, usually the saphenous vein from the leg. However, in many cases, the use of the patient's own vessels is not practical because the veins are either damaged, diseased or are not available. In these cases, synthetic materials are used, but with unsatisfactory long-term results. It is still a continuing goal of researchers to develop prostheses which can successfully be used to replace or repair mammalian tissue, particularly blood vessels.